1. Field of the Invention
The present invention relates to the construction of a rotary vane type gas compressor to be used in a vehicle air conditioner or the like.
2. Description of the Related Art
In a gas compressor used to compress the refrigerant of an air conditioner or the like, a rotor equipped with a plurality of vanes is rotatably provided in a cylinder which is arranged in a compressor case and whose inner peripheral surface is substantially elliptical, and, with its rotation, the space divided by the vanes forms compression chambers repeating a change in volume, refrigerant gas sucked into the compression chambers from an inlet port being compressed and discharged from an outlet port.
FIG. 8 is a longitudinal sectional view of such a conventional gas compressor, and FIG. 9 is a sectional view taken along line 9xe2x80x949 of FIG. 8.
A compressor case 10 is formed by a housing 11 open at one end and a front head 12 mounted to the open side thereof. In the housing 11, a cylinder 40 with a substantially elliptical inner periphery is arranged between a front side block 20 and a rear side block 30, and a rotor 50 equipped with a plurality of vanes is rotatably provided inside the cylinder 40.
A rotation shaft 51 rotating integrally with the rotor 50 extends through the front side block 20. Its forward end portion extends outwards from a lip seal 18 at an end wall of the compressor case, and its rear end portion is supported by the rear side block 30. An electromagnetic clutch 25 having a pulley 24 is mounted to the forward end of the rotation shaft, and torque from a crank pulley of an engine (not shown) is received.
As shown in FIG. 9, in particular, the rotor 50 has around the rotor rotation shaft 51 a plurality of radially extending vane grooves 53 arranged circumferentially at equal intervals, with vanes 58 being slidably attached thereto. During the rotation of the rotor 50, the vanes 58 are urged toward the inner peripheral surface of the cylinder 40 by the centrifugal force and the hydraulic pressure applied to the bottoms of the vane grooves 53. The interior of the cylinder 40 is divided into a plurality of small chambers by the rotor 50 and the vanes 58, forming compression chambers 48 repeating changes in volume as the rotor 50 rotates.
Formed between the front head 12 and the front side block 20 is a front side suction chamber 13 equipped with a refrigerant gas suction port 14.
The front side block 20 has an inlet port 22 establishing communication between the front side suction chamber 13 and the compression chambers 48.
Formed between the closed side of the housing 11 and the rear side block 30 is a discharge chamber 15 equipped with a refrigerant gas discharge port 16.
The cylinder 40 has, in its outer periphery and near the shorter diameter portion, discharge chambers 44 in the form of cutouts, and the corresponding portions of the cylinder constitute thin-walled portions. Outlet ports 42 are provided in these thin-walled portions. The outlet ports 42 are equipped with reed valves 43.
The refrigerant gas discharged from the outlet ports 42 is discharged into the discharge chamber 15 by way of the discharge chambers 44 and an oil separator 38.
The inlet ports 22 and the outlet ports 42 are respectively provided at two positions along the periphery of the cylinder so as to be symmetrical with respect to the rotation axis of the rotor.
When the rotor 50 rotates, the refrigerant gas flowing into the gas suction port 14 flows by way of the front side suction chamber 13 and the inlet ports 22 before it is sucked into the compression chambers 48. And, after being compressed in the compression chambers 48, it is discharged from the outlet ports 42 and flows by way of the discharge chamber 15 before it is supplied to the exterior through the refrigerant gas discharge port 16.
In such a conventional gas compressor, vibration is generated in the driving state in which the rotor 50 is rotated, and this vibration is often propagated to peripheral equipment including piping leading to an evaporator or a condenser connected to the gas compressor, thereby generating noise. FIG. 10 shows raw data obtained through measurement during operation of a conventional gas compressor, showing how the gas compressor generates a vibration acceleration component.
In FIG. 10, the horizontal axis indicates time and is graduated to 10 ms, and the vertical axis indicates acceleration and is graduated to 20 m/s2. In the vibration acceleration measurement, an acceleration sensor was fixed to the mounting portion of the compressor for a vehicle (as indicated by the shaded portion of FIG. 8) so that the acceleration sensor is positioned close to the vehicle, and the acceleration component in the direction of the rotation axis of the gas compressor was detected. The rotating speed of the gas compressor was set to approximately 1190 rpm on the assumption that the engine idling speed was transmitted.
From this raw data, it can be seen that a vibration acceleration of an amplification of approximately 80 m/s2 is generated at an equal interval of approximately 5 ms. When heard at the time of measurement, it is felt as a noise of a frequency of approximately 200 Hz.
Upon examination of the cause of the vibration, frequency analysis of the vibration waveform indicated appearance of very conspicuous peaks in the vibration of the basic compression (discharge) component of the gas compressor, and it was found out that this resonated with the peripheral equipment to thereby cause noise.
More specifically, in a gas compressor with five vanes, which has two outlet ports, compressed refrigerant is discharged ten times in one rotation of the rotor, and the resultant vibration constituting the basic component is obtained by multiplying the rotating speed of the rotor by ten.
In view of the above problem, it is accordingly an object of the present invention to provide a gas compressor which prevents a vibration with conspicuous peaks from being generated at minute equal time intervals during rotation of the rotor, thereby preventing generation of noise.
Since the basic component of the vibration generating peaks is consistently proportional to the rotating speed of the rotor, it is possible to restrain generation of peaks by destroying this consistency. Thus, in a first aspect of the present invention, there is provided a gas compressor of the type in which a rotor supporting a plurality of vanes in individual vane grooves is rotatably provided in a cylinder with a substantially elliptical inner peripheral surface arranged in a compressor case, the spaces obtained through division by the vanes serving as compression chambers, and the gas compressed in the compression chambers being discharged from an outlet port formed in the side wall of the cylinder to a discharge chamber outside the cylinder, wherein the openings of the vane grooves are arranged circumferentially at unequal intervals on the outer peripheral surface of the rotor.
In a second aspect of the invention, to arrange the openings of the vane grooves at unequal intervals, the directions of the vane grooves are determined such that they are at unequal angular intervals.
In this regard, according to a third aspect of the invention, it is possible to keep constant the distance between the center lines of the plurality of vane grooves and the rotor center.
In a fourth aspect of the invention, the distances between the respective center lines of the plurality of vane grooves and the rotor center are made unequal to each other.
In this regard, according to a fifth aspect of the invention, it is possible to determine the respective directions of the plurality of vane grooves such that they are arranged at equal angular intervals.
In a sixth aspect of the invention, the number of vane grooves is five, and the respective directions of the vane grooves are determined such that the respective angular differences between at least three adjacent compression chambers are not less than 5 degrees.
And, in a seventh aspect of the invention, the angular interval between the vane groove directions is set so as to range from 50 to 120 degrees.